Spark, supercharger, and throttle control



Nov. 13, 1945.

c. F. SCHORN SPARK, SUPERCHARGER, AND THROTTLE CONTROL 7 Sheets-Sheet 1 Filed Nov. '16, 1942 KWZ 17 50502 2:

INVENTORV Nov. 13, 1945. c. F. SCHORN 2,389,003

SPARK, SUPERCHARGER, AND THROTTLE GONTROL Filed Nov. 16, 1942 7 sheets-sheet 2 INVENTOR.

.1 1 Z J j Nov. 13, '1945.

C. F. SCHORN SPARK, SUPERGHARGER, AND THROTTLE CONTROL Filed Nov. 16, 1942 7 Sheets-Sheet 3 h mk mim N WA Nov. 13, 1945. c. F. SCHORN 2,389,003

SPARK SUPERCHARGER, AND THROTTLE CONTROL Filed Nov. 16, 1942 7 Sheets-Sheet 4 -=15 B1319 ear INVENTOR.

Nov. 13, 1945. "c. F. SCHORN 7 SPARK, SUPERCHARGER, AND THROTTLE CONTROL Filed Nov. 16, 1942 j v She'ets-Sheet s INVENTOR,

c. F. SCHORN SPARK, SUPERGHARGER, AND THROTTLE CONTROL Filed Nov. 16, 1942 '7 Sheets-Sheet 6 INVENTOR.

Nov. 13, 1945. c. F. SCHORN SPARK, SUPERCHARGER, AND THROTTLE CONTROL Filed Nov. 16, 1942 7 Sheets-Sheet 7 a Rw Patented Nov. 13, 1945 2,389,003 SPARK, SUPERCHARGER, AND THROTTLE CONT CarlF. Schorn, Detroit, Mich., assignor to George M. Holley and Earl Holley Application November 16, 1942, Serial No. 465,803

Claims.

The object of invention is to automatically control the engine manifold pressure as a function of speed such that at any given engine speed a definite engine power output will be obtained.

The control of the manifold pressurewill be such that with changing altitudes the power output of the engine will remain substantiallyconstant up to the altitude at which the carburetor is operating at wide open throttle.

An additional object is to substitute a pressure 10 device responsive to torque for the device responsive to manifold air pressure (M. A. P.) so that constant brake horse power would be obtained when operating at constant speed, regardless of whether the supercharger is operating in low or high blower ratio. The above presupposes, of course, that the demand for throttle opening to maintain the constant power does not exceed the carburetor wide open throttle position.

An additional object of this invention is-to automatically control the speed change of the supercharger drive responsive to M. A. P., speed of engine and altitude, so that the desired operating combination of power and speed will be continued as long as possible at the lowest possible supercharger speed and so as to obtain maximum fuel economy, especially when cruising lean."

An additional object is to control simultaneously and automatically the spark advance to give optimum engine operation.

A further object is to control in sequence two superchargers arranged in series, one ahead of the carburetor and one on the engine side of the carburetor.

In the drawings:

Fig. 1 shows diagrammatically the arrangement of the carburetor with reference to the supercharger when only one supercharger is used located between the engine and the carburetor, and

in which this supercharger can be driven at two speeds with relation to the engine speed.

Fig. 2 shows a similar arrangement in which there are two superchargers, one located in the air entrance to the carburetor and the second one between the. carburetor and'the engine. the first one being driven at one of two speeds or permitted to be idle; the second one being driven at a constant ratio to the engine speed.

Fig. 3 is a diagram showing a typical curve of desired sea level engine performance as controlled by the power control and also showing the performance of the control for a selected combination of engine speed and power with changing altitudes when the power control is used with the single two speed supercharger illustrated in Fig. 1.

Fig. 4 is a diagram of control performance showing the operation of the control with changing altitudes for a selected combination of engine speed and power whenthe power control is used with the two superchargers illustrated in Fig. 2.

(Cl. I'm-135.6)

Fig. 5 shows the preferred form of my invention to be used in conjunction with the arrangement shown in Fig. 1.

Fig. 6 shows the alternative construction when my invention is used in connection with the two superchargers as arranged in Fig. 2.

Fig. 7 shows a modification of Fig. 5 in'which the torque developed by the engine is substituted for M. A. P. as a factor in the control of my device.

Fig. 8 shows the means for developingthe fluid pressure proportional to the torque developed by the engine.

In Fig. 1 the arrangement of the supercharger vI03 represent the drive shafts for the supercharger ml which is shown driven by a belt I02. The shaft I03 revolves at a higher speed than the shaft I00. A clutch I04 is adapted to engage with the.

clutch I05. Hence, if the lever M3 is moved counter-clockwise, the supercharger IN is driven at a higher speed, an overrunning clutch (not shown) being provided between the shaft I00 and the clutch I05, to permit clutch I05 to run faster than shaft I00. A carburetor throttle I01 and air entrance I08 are shown diagrammatically leading to the supercharger I0 I The lever I43 is connected through link I I5, lever I05, with clutch I04, so that the counterclockwise motion of lever I03 causes clutch I04 to engage with clutch I05.

The throttle I0'I is controlled by a throttle lever I35. This throttle lever is controlled by the broken. link I35, I31 which is controlled by the manually operated lever I38. At the point of juncture of the broken link I36, I31 there is another link I39 which is connected through a link I40 with the element 350 which is the throttle control element of Fig. 5, the functioning of which will be described later. A radius rod MI is provided for obvious reasons and is joined at the point of Juneture of the links I39 and I40.

A link I0 is connected to lever I38 and this is the pitch control lever I0 shown in Fig. 5. The element 53 of Fig. 5 causes the speed of the supercharger to change. It is connected through the link I42 to the bell crank lever I43 which is connected to the link II5, the operation of which causes the clutch I04 to engage with the clutch I05, and thus cause the supercharger propeller IOI to increase in speed, as already described.

The lever I38 is connected by a link 400 to the pilots cockpit control so that one. lever in the pilot's hand controls:

In order to accomplish (a) the following elements are added:

A valve 00 (Fig.5) is moved by the rod I18,

when the lever I33 is moved clockwiseto close the throttle and to reduce speed. When the lever I33 engages shoulder I19 on rod I13, the sprin I is compressed and the lever I" is also moved clockwise. This opens the valve 00 into the position in which valve 00 is shown in Fig. 5. When in this position, the element 300 is pushed down by the compression spring which engages with the piston 59 hence the piston 59 of the mechanism shown in Fig. 5 is thus rendered inoperative and the throttle is manually closed from the throttle position corresponding to the engine speed of 1200 R. P. M. down to the idle position of the throttle.

To the left of Fig. 3 is shown the manifold air pressure in inches of mercury at different revolutions per minute of the engine at sea level. Beginning at the point P where we have 30%" of mercury at 1000 R. P. M. and up to the point Q where we have 28" of mercury at 1800 R. P. M., I arrange to have a constant brake mean eflective pressure of 135 lbs. per sq. inch. From Q to R which is labeled propeller load, the torque increases and with it B. M. E. P. to 198.8. At the same time, the R. P. M. increases to 2300 and the manifold air pressure increases to 40" of mercury. At this point the engine develops 1500 H. P. which is the maximum H. P. available for take off, but in flying the plane immediately after "take 0 the power is lowered and maintained at or below the point A, that is, below 1200 H. P.

in order that the engine is not overstressed and s that excessive fuel is not used.

Referring to Fig. 3, if the manifold air pressure is held constant at 34.7 of mercury the power increases with altitude due to the effect of low atmospheric pressure on-the escape of the exhaust gases. Beginning at the point A, and assuming that the M. A. P. of 34.7" of mercury which exists at point A is maintained constant automatically by opening the throttle I01 in Fig. 1 by the linkage I4I, I40, I39, I31, I39, I36, I35, which linkage is operated by the mechanism shown in Fig. 5, specifically by the element 360, at point B the throttle I01 will be wide open, the power will have risen to 1250 H. P. at the rate of approximately 1% per 1000 feet, due to the fall of 4%" mercury in back pressure. From B to C is a condition which the pilot describes as one in which he has run out of throttle. At C the throttle remaining wide open, the power has fallen to below 1100 H. P., and the altitude is now 8800 feet. At this point the clutch I04 automatically engages with -the clutch I05, Fig. 1. This engagement is brought about by the linkage I42, I43, 5, I06, I04, I05, which linkage responds to the element 53 of the mechanism shown in Pig. 5 which for this case is calibrated to shift at point C. The supercharger IOI now revolves at a higher rate of speed for the same speed of the engine, as shaft I03 rotates faster than shaft I00, and raises the manifold air pressure above 34.7" of mercury, whereupon the linkage I35, I36, I31, I38, I39, I40, I4I, becomes operative to close the throttle, responding to the element 360 of the mechanism shown in Fig. 5, and the manifold air pressure is once more restored to 34.7" of mercury. Again as the plane climbs, the throttle I01 opens to maintain this M. A. P. at 34.7" of mercury until at point D 12,500 feet altitude, the throttle I0! is once more wide open and the power is 1125 at point D, after which the power falls along the line DJ until the ceiling is reached.

Referring to Fig. 3, the line AF indicates constant power from sea level to 6000 feet. At A .the power will then shifted into high the manifold air pressure will be 34.7" of mercury, that is, the point where the line AF extended to theleft intersects the line 2100 Indicates the pressure corresponding to the point Y on the sea level performance line PQR. At F corresponding to 6000 feet altitude, the manifold air pressure will be 33" of mercury with the supercharger I0 I, Fig, 1 running at the low speed. At the point F the throttle I01 will be wide open. From F to G the throttle will remain wide open and the barometric pressure of the atmosphere will fall ,from 24" of mercury to 19.6" of mercury (11,300 feet altitude), and the engine power will therefore fall from 1200 to 980 H. P. At this point G the speed of the supercharger will be automatically increased by the action of the elements 53, I42, I43, IIS, I06, I04, I05, (Fig. 1), and the throttle is closed by the action of the elements 380, I40, I39, I36, I35 of Fig. 1, to prevent excessive supercharger or manifold pressure.

From G to I, the throttle IN is gradually reopened by the action of the elements 360, I40, I39, I39, I35 responding to the mechanism shown in Fig. 5. and the power remains constant at 980 H. P. At the point I-the throttle I0? is again wide open and the horse power again falls along the line LI and continues to fall as the altitude increases until the ceiling is reached.

Let us assume that the engine, shortly after taking on, is throttled to a cruising power," so that only 900 H. P. is developed at point X at sea level at 1900 R. P. M. Extending the line KL to the left, the line PQR is intersected at point Z corresponding to 29.5" mercury M. A. P. developed at point K at sea level at 1900 R. P. M. This 900 H. P. is held constant to the point L which is 10,000 feet when the throttle is wide open. The throttle will then remain wide open to the point M, at which point the second speed of thesupercharger will be automatically engaged and the power will remain constant along the line M0 until wide open throttle is reached. It will be noticed that when running along the line KLM the supercharger is revolving at a relatively low speed up to 15,400 feet.

Assuming that there is no compensation for altitude, then the M. A. P. will be maintained constant at 29.5" mercury, and therefore the power will increase from 900 H. P. to 990 at the point S, at which point the throttle will be wide open and from then on the power would decline along the line SLT when the second speed of the supercharger will be automatically engaged since it is now assumed that the engine will satisfactorily operate at this M. A. P. and the supercharger is now calibrated to shift at point T and increase along the line TU as the M. A. P. will be maintained constant at 29.5". At U the throttle will again be wide open with the-engine running at 1900 R. P. M. The power would then decline along the line UV.

It will be noted that the second speed comes into action at 11,000 feet whereas the transition from first to second speed indicated at point M occurs at 15,400 so that between 11,000 and 15,400 the line TM represents more economical operation than the line TU.

In Fig. 1, when following the -line AFGIJ of Fig. 3, the lever I00 is rotated clockwise when we arrive at the point G and the supercharger is speed. The M. A. P. which was 27" at the point G in low blower immediately rises to 32". Since the power output remains the same, the increase of the manifold pressure from 27" Hg in low blower to 32" Hg in high blower is an indication of the increased power required to drive the supercharger at a greater R. P. M.

pressure enters the device through the lower passage." and escapes from the upper passage When the torque is the basis for controlling.

rather than M. A. P., the H. P. line AF is continued to the point W, Fig. 3 so that the horse power is maintained constant at 1200 H. P. up to an altitude of 10,800. This shows an advantage of torque control over M. A. P. control, of

Operation of control mechanism (Figs. 1 and The valve 60 is opened at low power and speed, at which point the engine speed and power respond simply to the throttle. The governor II is not operative at engine speeds below approximately 1200 R. P. M. The propeller at the speeds below 1200 R. P. M. is in the pitch determined by the pitch required to develop the manifold pressure required at 1200 to produce the desired performance By the time we get below 1200 R. P. M. for example, the manual control I38 acting 3|. The lower passage communicates with the servomotor valve 23 which permits oil under through link I18 and lever II'I opens the by pass valve 60 making the automatic mechanism controlling the element 360 inoperative. Thereupon the sole control after I38 engages stop I19 of both engine speed and manifold pressure is the throttle because the speed of the engine has become tm) low for effective propeller governor operation.

As we rotate the lever I38 anti-clockwise to open the throttle, we release the lever Ill and render the automatic mechanism controlling 330 operative. We thereupon lose the manual control of the throttle and gain the automatic control. At the same time we gain manual control of the speed. Further counterclockwise motion of the lever I38 moves the link I0 so as to increase the manually selected speed of the propeller.

The pump I8 is driven at a speed proportional to the engine speed and is of the positive displacement type and pumps a given quantity of oil per revolution through the orifice 369. This pump, therefore, creates pressures acting on the diaphragm III, which pressure varies as the square of the selected R. P. M. In order that this should be true, fluid is maintained at a constant temperature by thermostatic means 20, 2I and 22, 20 being a battery, 21 a heating coil, and 22 a strip of bimetallic metal. These are well known elements in general use and will maintain substantially a. constant viscosity because they will maintain the fluid rotating in the pump It at a constant temperature.

The diaphragm I3 controls-a servomotor valve 23 shown in its neutral position. When the valve 23 rises it compresses a spring 21 which is pivotally supported on a lever I30, which lever is connected on its left and through a slot with the piston rod I3I. The piston rod I3I is connected with the piston 22 which is controlled by oil under pressure which is supplied through the passage 29 and escapes through the passage 30. When the piston 24 rises due to a rise in the valve 23 in response to an increase in speed causing an increase of pressure on diaphragm I3, oil under pressure to be effective either above or below the piston 24, depending on the position of the valve When the piston rod I3I rises. it compresses the spring 21 and restores the valve 23 to equilibrium, that is, it moves the valve 23 back into its neutral position. Hence it follows that at every position of the link It there will be a deflnite position for the rod IN. The rod I3l is I connected with the lever 23 which rotates a shaft- Obviously, the rod I0 could be directly connected to the lever 23 so that atevery speed of the engine there would be a definit position of the shaft 25. However, in that case any manufacturing errors in the production of the propeller control would have to be corrected by suitable calibration of the unit shown in Fig. 5, which would then cease to be an interchangeable unit and would have to be calibrated for each installation. In order to make these units interchangeable without the need for calibration noted above, it is necessary to separate the speed control of the shaft 25 from the pitch control of the propeller.

In Fig. 5, I0 is the manual controlfor the speed of the engine connected to the manually operated lever I38 (Fig.1). II and. I2 are the rack and pinion which control a spring I3, which controls governor weights It, which, in their turn, control the servomotor valve I5, which acts as a slide valve to adjust the pitch of a propeller by means of hydraulic pressure, which is transmitted through a pipe it from the servomotor valve I5 to the automatic mechanism (not shown) incorporated in the hub II of the propeller.

For every position of the red It there must be a definite number of R. P. M. of the engine. Hence, the speed control rod I0 selects the speed at which the engine is to run and by means hereinafter described it is possible for the pilot to operate the plane with a single control connected to lever I38 shown on the drawin Fi 1 that is, he simply selects the speed and the automatic device shown in Fig. 5 which is the subjectof this invention selects the spark advance, decides when a change of supercharger gear drive is to be made and when the throttle is to be opened or closed.

Obviously, an engine driven centrifugal governor corresponding to the governor shown in the lower left hand corner of Fig. 5 could be substituted for the hydraulic governor shown in the lower right hand corner. In that event elements similar to I3, I4 and I5 would be substituted for the elements I8 and I9 and the valve 23 would then be moved by centrifugal weights instead of by the diaphragm I3.

The operation of the shaft 25, Fig. 5 is as follows:

The rotation of the shaft 25 when viewed from the right is clockwise. In other words, the shaft 25 is actually located below the plane of the drawing, although it is shown as though it were in the plane for the purposes of illustration.

The rotation of the shaft 25 compresses a spring 43 by means of a cam 32. A partially evacuated capsule assembly 33 is thus moved downwardly and carries with it the servomotor valve 34. This permits high pressure oil to flow from the passage 28 and to travel through the passage 35 and become effective on the upper side of the piston 36, pushing the spark control rod 31 down to advance the spark, at the same time compressing the spring 38 through a link I32, which restores the valve 34 to its neutral position. Low pressure oil from below the piston 36 escapes through the passage 39 through the ports in the valve 34, and so out through the passage 3|. The chamber 40 containing the capsule assembly 33 communicates with the engine inlet manifold through a pipe I33, chamber 64 and pipe I34 connected to the supercharger of the engine, and istherefore maintained at the pressure of the air entering the engine cylinders.

It has been found desirable that an increase of speed should cause the spark to advance. It has also been found desirable that this tendency of the spark to advance as the speed increases should be counteracted by the eifect of the increase in manifold air pressure requiring a later spark. For this reason, an increase of pressure in the chamber 40 causes the capsule assembly 33 to contract and permit valve M to rise to retard the spark. Hence the advance of the spark is determined by two variables-namely, the R. P. M. of the engine and the M. A. P.

The clockwise rotation of the shaft 25 also rotates the cam ll, the rotation of which releases the compression of the sprin 42 and causes the capsule assembly -46 to rise, carrying with it the valve 60. The upper two elements of the capsule are marked 48 and communicate through a passage 45 with the inlet manifold pressure. The

capsules 46 are connected to the lower two elements to which are partially evaculated capsules. This compound capsule assembly 44-00 is contained in the chamber 07, which chamber is maintained at atmospheric pressure. The capsule assembly 4446 is connected to the supercharger servo-control valve 48 which is in contact with the bell crank lever 49:, which is springloaded by the tension spring 50 which is anchored at I.

By this arrangement, when the downward pressure on the valve 58 is increased, either due to a decrease in atmospheric pressure or an increase in manifold pressure, or a decrease in engine speed, there is an increased downward pressure on the bell crank lever 49, stretching the spring 50 over dead center,-so that the valve 48 suddenly moves downwardly when a critical relationship between R. P. M., manifold pressure and atmospheric pressure is reached. This sudden descent of the valve 88 permits high pressure oil from the passage 28 to enter below the piston 52 through the passage 366 to move the piston 52 upwardly. At the same time oil escapes from above the piston 52 through the passage 36! and finally out of passage 3|. This piston is connected with the cross head 53 which travels upwardly when the supercharger is shifted from low to high blower position by linkage I42, H3, H5, I06 of Fig. 1.

When the combination of speed, altitude, and M. A. P. is reached at which it is desirable to change the rate of rotation of the supercharger,

the rod H5 (Fig. 1) moves to the right, the clutch I04 engages with the clutch I05, the shaft I03 drives the supercharger IOI in place of the shaft I00. There is an overrunning clutch (not shown) which permits the shaft I03 to drive the belt I02 faster than the shaft I00 drives the belt I02. This gives the desired two stage blower drive.

Rotation of the shaft 25 also causes the cam 54 to vary the load on the spring 55, thus the capsule assembly 56 located in the chamber 64 is moved. This chamber 64 is maintained at manifold air pressure through the pipe I. The descent of the capsule assembly 58 causes the power control servomotor valve 51 to move downwardly, permitting oilunder pressure from the passage 28 to pass through the passage 68 and so beneath the piston 59, causing the piston 58 to rise and to move the cross head I60 connected to the carburetor throttle III! of Fig. 1 by mechanism so as to open the throttle I01 of Fig. 1. The low pressure oil above the piston escapes through passages 66 and 3|. A diaphragm 0| connected to the valve 51 is subjected on its upper face to atmospheric pressure through Passage I15 and manifold air pressure acts through passage I14 on its lower face. A tension spring 62 anchored to an eccentric support 63 permits a variable load to be applied to the capsule assembly 56 through the valve 51. The combination of diaphragm SI and capsule 56 enables the M. A. P. to fall with increasing altitude to maintain constant horsepower. A M. A. P. of 33" mercury at 6000 feet permits the engine to develop the same horsepower as is developed at sea level with a M. A. P. of 34.7" mercury.

An increase in manifold air pressure above that called for by the combined effect of the cam 58, diaphragm SI and spring 62 caused the valve 5'5 to rise from its neutral position and thereby cause the throttle l0! to close to reduce the M. A. P. to bring the valve back to the neutral position. The effect of a decrease in atmospheric pressure with a. given M. A. P. has a tendency to also close the throttle by producing a pressure difierential across diaphragm 85 which produces thesame effect on valve 5'! as excessive M. A. P. It thus results that at any given position of the shaft 25, the M. A. P. decreases with altitude to maintain constant horsepower along the line AF of Eig. 3, which is the result desired.

Operation-(Figs. 1, 3 and 5) The pilot moves the cockpit control lever toward the open position. The pinion and rack are moved by link I0 to select a sufiiciently high R. P. M. of the engine to get off the ground. The eifect of this R. P. M. on the pump I8 and diaphragm I9 positions the piston 24 and rotates the shaft 25, which has a definite position for every speed selected by the pilot. The shaft 25 having rotated into it's operative position, the spark is advanced due to the downward movement of the shaft 31. This downward movement reflects an increase in R. P. M. At the same time, the spark is retarded by the simultaneous increase in M. A. P. Hence, the spark timing refiects the influence of both speed and load. The increasing speed increases the advance; the increasing load decreases the advance in a well known manner. Hence, for any given speed and any given manifold air pressure, there is a deflnite spark advance.

Consider next the end cam 54 which controls the element 360, Fig. 5 which causes the throttle I01, Fig. 1 to open and close to give the desired M A. P. determined by the contour of the cam 54. Let us assume that the plane is climbing to 6000 feet. As the plane-ascends at a constant R. P. M. the decrease in atmospheric pressure would cause a fall in the M. A. P. should the throttles remain at the sea level opening. This decrease in M. A. P. causes the bellows 56 to expand lowering the valve Bl. This, allows oil under pressure to pass through passage and beneath piston 09. The piston raises element 000 and through the mechanism shown in Fig.

1 opens the throttles I01 until the M. A. P. foe-- and thereby reduces the M. A. P. required to place the valve in its neutral position. By this means. a sufllcient reduction in M. A. P. occurs with increasing altitude to offset the effect of the reduction of the back pressure on the engine exhaust and thereby maintain substantially constant B. H. P. Referring -to Fig. 3, if the plane starts its climb at sea level with the engine operating at 34.7 M. A. P.and 2100 R. P. M. it would when two superchargers are used one supercharger IOI of Fig. 2, is located between the carburetor and the engine and this one is run at a constant speed ratio and is always in gear.

An auxiliary supercharger I09 is located in the air entrance I08 leading to the carburetor throttle I01. This auxiliary supercharger may be idle or operated at low speed ratio or at a high speed ratio.

In Fig. 4 starting with the power at point A corresponding to 1900 R. P. M. and 850 H. P. and running with "a manifold air pressure of 29", which manifold air pressure is automatically maintained constant, at the point B we have an increase of 50 horse power to 900 corresponding to an altitude of 4200 feet and a barometer of approximately 25 of mercury. At this point climb along the constant R. P. M. .curve AF and would reach the carburetor wide open throttle position at approximately 6000 feet. The M. A. P. would have fallen from 34.7" Hg at sea level to 33" Hg at 6000 feet. The plane would then continue to climb with the engine operating in low blower along the constant R. P. M. line FG until 11,300 altitude is reached. The manifold pressure will have dropped to 2'7" Hg and the power will have dropped to 980 B. H. P.

At 11,300 feet it is desired to shift from low speed supercharger operation to high speed operation. At the operating speed of 2,100 R. P. M. the cam I, Fig. 5 definitely locates the top of the capsule assembly 46. The bottom position is definitely determined by the pressure in the chamber 41, that is to say, by the atmospheric pressure which efiects the length of the entire capsule assembly 4446 and by the M. A. P. which eflects the length of the element 40. The net result is that the supercharger control valve 08 exerts increasing pressure on the bell crank lever 49 which rotates clockwise and snaps over under the influence of spring 50, when it comes over dead center. The piston 52 immediately moves up and shifts the supercharger drive from low to high speed and the plane continues to climb with the engine operating in highblower at substantially the same B. H. P. that was available just before the shift.

It is to be noted that the operation in high blower at 11,300 is at 32" M. A. P. The increase in M. A. P. in high blower over the M. A. P. in low blower to produce the same B. H. P. is an indication of the less eiilcient operation in high blower and demonstrates why the shift should not be made at an altitude lower than that at which the 'B. H. P. in high blower equals the B. H. P. in low blower; for instance, if the shift to high blower had been made at 10,000 feet instead of 11,300 feet, approximately 60 B. H. P.

less would be obtained in high blower than in the low blower operation asshown by the broken lines GHG, Fig. 3. When descending the reverse action takes place shifting the supercharger from high speed to low speed. The altitude at which the shift will take place will be somewhat lower than 11,300 of course, this being inherent in the design.

When climbing above 11,300 feet the engine will operate along the line G-I. At I the wide open throttle position of the carburetor is reached and operation takes place along the constant speed decreasing power lines IJ.

the throttle I0! is wide open and the B. H. P. therefore, as the plane climbs, declines. on the line BC until the B. H. P. falls to 800 at the point C.

This occurs at 8000 feet altitude, barometer 22.2" of mercury. At this point the auxiliary blower I00 is engaged in low speed ratio and the throttle I26 which has been open up to this point moves to a partially closed position and the manifold air, pressure is again restored to 29" of mercury. Thereupon the power rises along the broken constant M. A. P. line CD. At the point D we again have 850 B. H. P. and we have an altitude of 15,500 feet and barometer of 16 of mercury. At this point both throttles are wide open, the power thereafter declines until the point E is reached, at which time the second speed of the auxiliary supercharger becomes operative and the auxiliary blower throttle again moves to partially closed position, and the power increases along the broken line EF with th manifold air pressure being again maintained constant at 29" of mercury. At the point F we have a B. H. P. of 770, we have an altitude of 29,200 feet and we have a barometer of less than 10" of mercury. At this .point both throttles are again wide open and the B. H. P. declines along the line FG as the plane continues to climb until th ceiling is reached for this condition.

Repeating the process and assuming a constant power is maintained in the events that occur after the point C is reached, we have the following conditions:

At the point C when the first speed of the auxiliaryv supercharger I00 becomes operative. the power is maintained constant at 800 H. P. along the. full line CI by varying the pressure in the air entrance. At the point I we have an altitude of 17,000 feet and a barometer of 15.6" of mercury. The power declines along the line 1E and power is 730 at the point E, the altitude is 19,000 feet, the barometer being 14.4. The

power then remains constant along the line EJ.

through the belt I02 at a constant ratio, so that in this, case the supercharger IOI operates at a fixed speed for any given R. P. M. of the engine.

I0'I indicates the carburetor throttle with throttle lever I35. I00 indicates the air entrance on the engine side of a second supercharger I00 which is driven by a belt IIO. Located in the air The operation of the blower I08 tends to raise entrance there is an lntercooler II8. to which the pressure in the air entrance I08 and therecooling air enters at II I and escapes at H8. The fore in chamber 284 which tends to collapse the supercharger. I08 is-driven by a shaft II 2, and evacuated bellows 288 and to move the servoin the position shown it is idle. There are two motor valve 000 to the left, which moves the speeds at which the shaft II2 can be run. When rod 221 to the right to close the throttle I28 the link III moves the gear I20 so as to engage until the inlet pressure to the carburetor is with the gear I2I mounted on the shaft I00, equal to that for which the control is set in this the shaft H2 is driven through the gears I 22, case about 25.5" Hg. The action of the servo- I22. Further movement of the link II8 causes 10 motorisasfollows:

the gear I22 to be disengaged from the gear I23, As the pressure in 288 increases, the valve 200 the gear I28 then becomes engaged with the gear moves from the neutral position shown to a posi- I28, and the speed of the supercharger I08 is tion to the left ofthe neutral position. In this increased. Meanwhile the gear I20 remains in second positiomoil enters under pressure from a gear with the gear I2I. Therefore, there are passage 228 through an annular passage around thre positions for the link II8-the position the valve 300 through the passage 208 to the left shown In which the supercharger I08 is in operhand side of the piston "288. Thi oil pressure .ative; the second position when the gear I22 pushes the piston 259 over to the right, pushes the meshes with the gear I22, and the third position link 22! to the right and closes thevalve I28 by when the gear I28 meshes with the gear I 28. We clockwise rotation of the lever 228. Meanwhile thus have three conditions: one where the superoil escapes through the passage 288v through the charger I8I operates alone; secondly, where the center of the valve 800 to the oil outlet 22I. The supercharger I80 operates at low speed in conclosing of the valve I28 restores the pressure of junction with the supercharger 'l0I; and thirdly, 25.5" of mercury in the chamber 288 because at where the supercharger I00 operates at high speed 25 this pressure the system is in equilibrium. AI; in conjunction with the uperchar e I01. The 25.5" of mercury, the valve 800 then return subthrottle I28 which leads to the supercharger I09, stantially to the neutral position shown. Just should be open when the supercharger I08 is enough pressure is admitted to the left hand side idle. Air is admitted through the valve I28 of the piston 259 toovercome the spring 201. In through the idling supercharger I 08 and also past 30 other words, the valve I28 floats so as to maintain the spring loaded valve I21 past the carburetor a pressure in the chamber 284, that is to say, in throttles I01. When the supercharger I08 is in the air entrance I 08. 01 25- 01' r ryoperation the valve I28 operates from partially As we climb above 8000 feet, the horse power open to open position and the valv I2! i lo d, climbs on the constant M. A. P. line from C to D In the upper left hand corner of Fig. 2 is shown ig. 4) and reaches 850 H. P. 15,500 feet. From a servomotor which controls the throttle I26, the point C to the point D the throttle I01 rewhich throttle I28 controls the air supply to the mains wide open. n h valve n gradually supercharger I08. A description of this servoopens un it is ide o en at point Thereafter motor and its operation is as follows: t e P w r f ls f D to ng 8 P B A partially evacuated eapsule 258 is shown 40 730 at point E, that is at about 19,000 feet. (At located in chamber 200 connected through a the pointEconditions that occurred at pointCare pipe 23! with the air entrance I08 on the engine repeated. that s to say. the link H9 again moves side or the supercharger I09. The device is tc t. th g ar I22 is disengaged from the shown in the position it assumes just before point gear I23, and the se r 4 ges with the 8 8 C of Fig. 4, that is Just before the gear I20 en- I25, but the gear I20 remains in mesh with the gages with the gear I2-I. In this position the rod sear HI.

9 holds the valve 200 in the wide open position The net result i an increase in sp d of h by means or a push rod 38! which engages with blower I 09 which means anincrease of pressure a lever 382 which is mounted on the valve 200. n e ham er I08 a ve 6 mercury, wh A spring 382 causes the lever 383 to follow the means an n e of Pr re in the chamber rod 88I so that when the gear I 20 engages with 268, which means that the valve 300 once more the gear I 2| the valve 200 moves to the closed moves tothe left and the action already described position and the mechanism operating I26 bei repeated. The valve I28 is again Partially comes operative. In the position just before the closed so as to maintain in the chamber I08 9. point C ofl lg. 4 already referred to, the valve pressure of 25.5 of mercury.

288 being wide open, the pressure on both sides The operation described with reference to the ofthe servomotor piston 258 is equal. Therefore, change from C to D is repeated as the engine the piston 289 is pushed over to the left by the m s along the line that is to say, it clim s compression spring 301. Hence, the link 22! pulls from 19,000 feet to 29,200 feet with the throttle the lever 228 to the left and therefore th throttle I 28 gradually returning to its wide open position. I28 is held wide open. At the point F the throttle I01 and the throttle From the point B back to sea level at A, the I28 are both wide open and in the langauge of the power falls, the throttle I01 being controlled as pilots "we have run out of throttle and therefore. in Fig. 1. In this case, the control is not corhe power fa s rap ly a o e the e G a d rected for altitude but is designed to maintain continues to fall until the ceiling of the Pl ne is a constant manifold air pressure at 29". reached.

Returning to the condition corresponding to In order to obtain the performance correspondthe point C of Fig. 4 when the plane ascends ing to the horizontal lines CI and EJ of Fig. 4, it is above 8,000 feet altitude, then the gear ennecessary tomodify this arrangement bymeans of gages with the gear m and the gear I22 with a di p ra m 0 s d ap a m is connected the gear I22, the link II9 being shifted to the to the end of the valve 800 and is subjected to the right, and when this happens the valve 200 is same pressure as exists in the chamber .288

closed and the. servomotor becomes operative and through the passage .302. This diaphragm is subthe supercharger I08 starts to function at its .iected on its left hand face to the atmospheric lower speed ratio. 7 pressure through a passage 308.

An adjustment 300 is provided for the valve 800 which adjusts the zero position of the evacuated element 256. Assuming the engine is operated at the point corresponding to C of Fig. 4, the moment the second supercharger I becomes operative at the speed determined by the gear ration I2I, I20, I22, I23, the pressure in I00 in- .creasesabove 25.5. When this happens the element 256 is compressed and collapses and the valve 800 travels to the left and then the piston 258 travels to the right, as already described. The valve I26 is thus closed until equilibrium is reached when the pressure in the chamber I08 is at a pressure less than 25.5 as modified by the action of the diaphragm 30 I.

The function of the diaphragm 80I is as follows: In climbing above point C on Fig. 4, 8000 feet, the atmospheric pressure admitted through 303 on the left hand side of the diaphragm 30I become lower than the inlet pressure existing in I08 which is transmitted through the passage 204 and 302. This pressure differential causes a load to act on the valve 300 which tends to compress the partially evacuated bellows 258. Therefore, this decrease is atmospheric pressure ha the same effect on the bellows 256 as an increase in air pressure in the air entrance I08 would have. The control therefore acts to close the valve I26 .or rather to move in the direction of closing which reduces the air entrance pressure until the valve 800 moves back into the neutral position shown. The area of the diaphragm 30! is therefore selected so that its influence 0n the pressure in chambers 2G4 and I08 is just enough to maintain the power constant along the line CI, Fig. 4.

Fig. 6 shows the automatic device required to change the Sp ed inthe two stage supercharger to obtain the performance corresponding to line ABCIEJG Or the line ABCDEFG Fig. 4 when climbing. .By this means, the rod 14 will be in the position marked C Fig. 6 before reaching the point C Fig.4. When the rod H9 is moved by rod 14 so as to engage the gears I20, I2I, I22, I28, the rod 14 is then moved into the position shown in full marked B which carries with it the rod II! from the position in which the rod H9 is shown in Fig. 2, which position corresponds to the condition just prior to point C of Fig. 4. When climbing, and the conditions correspond to the point C of Fig. 4, the mechanism shown in Fig. 6, specifically the rod 14, is just at the point of departing from the position marked C into the position marked B, which is the position illustrated in full lines in Fig. 6. When descending from above 8000 feet, when passing through the point C the change back does not occur at the same 8000 feet altitude, but is delayed somewhat because of the snap actioncontrolling the valve 8|.

In Fig. 6 the shaft 25, as before, rotates controlling cams. The cam II, for example, corresponds to cam M of Fig. 5.. However, there are two stages now and therefore a second cam marked In is required to control the second shift.-

The piston 12 corresponds to the piston 52 on Fig, 5 and the beam I3 to which it is connected corresponds to the sliding element 53 of Fig. 1. The rod 14 is the means whereby the two speeds of the auxiliary supercharger are controlled. The position 0 corresponds to the neutral stage, Fig. 4, that is to say, that portion of the chart ABC; the position 3 to the first speed that portion of the chart marked CIE, and the position marked A corresponds to the second speed, that is to the line EJG'. The left hand side of the beam I3 is connected through a slotted connection with the piston I5, the movement of which controls the second speed, or higher speed of the auxiliary supercharger I08. The first speed ratio of I00is indicated as CI of Fig. 4 and is controlled by the cam II which compressesthe spring I0 and also compresses the aneroid bellows 11. The two upper elements of this aneroid bellows ll communicate, through a pipe 18 with the pipe II8 which connects through pipe I34 with the supercharger .of the engine, that is to say, with the engine side of the supercharger IOI of, Fig. 2. Hence the two wper elements of the bellows 11 have supercharger pressure, or manifold air pressure, on the inside and are subjected to atmospheric pressure from the outside as the chamber IS in which the bellows "I1 is located is vented to the atmosphere through a passage 80.

The two lower elements of the bellows 11 are partially evacuated, for example, to a pressure of 10" of mercury and are thusresponsive to both temperature changes and pressure changes. The valve 8| is connected to the aneroid bellows through a spherical connection. The valve 0| is shown-just after it has admitted oil under pressure from the pipe 28 through the passage 82 to the top of the cylinder in which the piston I2 is located. In'other words, we assume that we have just passed the point C of Fig. 4.}1Fromthe bottom of the cylinder oil escapes t rough the passage 83', through the center of the valve 8|, to the low pressure outlet 8I.' Hence, as the plane'climbs above the level corresponding to the point C of Fig. 4, that is above 8000 feet, the atmospheric pressure admitted to the chamber I8 falls, the aneroid bellows I'I expands causing the valve 0| to descend to a point where the trip over mechanism passes through center and the piston I2 descends for the reasons already set forth and the rod M descends from position C to position B, making the first change from neutral to the first speed of the control of the auxiliary supercharger I09. In other words, H9, Fig. 2, moves to the right and gears I20, I2I, I22, I23 cause the auxiliary supercharger I09 to become effective. At the same time the valve 200 is closed, rendering the servomotor on the left hand side of Fig. 2 effective to control the air inlet valve I26.

As the plane continues to climb the pressure of the atmosphere continues to fall. The aneroid bellows 84 contained in chamber 19 and controlled by the cam I0 now comes into its effective position, and it, too, expands pushing down, in its turn, the valve 85 which when the valve descends, admits oil pressure through the annular port of the valve 85 to passage 86, and allows oil to escape through the center of the valve 85 and from the passage 81 from the underside of the piston 15 to the outlet passage 3|. Hence, the two ends of the beam 13 are moved at different stages so that there is an initial movement and a second movement, so that the two supercharger speeds can be successively regulated according to the altitude. Otherwise the operation of this is similar to that of Fig. 1.

Figs. 7 and 8Torque control Figs. 7 and 8 show the means whereby torque or rather a pressure responsive torque, may be substituted for manifold air pressure.

Fig. '1 is an outside view of Fig. 5 with certain modifications. For example, the diaphragm SI of Fig. 5 has been omitted. In Fig. '1, I50 indicates the chamber in which oil is present at a pressure responsive to the torque. This chamber communicates through a pipe I5I corresponding to the pipe I33 of Fig. 5 and this pipe communicates first to the chamber 54, second to the interior of the upper two elements N in the chamber 01, and finally to the chamber containing the evacuated element 33. By this means the torque pressure takes the place of manifold air pressure in all three chambers, that is, in the chamber 10, in the interior of element 04, and in the chamber 60 surrounding the evacuated element 58. Hence the operation will be almost the same as before, that is to say, as the torque increases the element 53 willbe contracted, the element 00 will be expanded and the element 33 will be contracted and the valves 51, 33, 33 will move so as to respond to an increase in torque, and the operation will be similar to that described for Fig. 5.

In order to obtain low operating pressures corresponding to the high torque pressure, it is necessary to couple the chamber I50 with the device operating the torque indicator I52. This torque indicator is operated as follows:

A torque lever I53 whose relation to the engine is indicated in Fig. 8. is coupled to two pistons I54, I55. These pistons are connected through the links I50, I51 with the lever I53. They reciprocate in the cylinders I58 and I59. Oil under pressure is supplied through the pipe I50 and the valve II admits oil under pressure to the cylinders to balance the torque, that is to say, when the pressure is higher than that required to balance the torque, the valve IOI cuts 01! the admission of oil under pressure from the pipe I60. The element I53 in Fig. 8 is connected to an engine shown diagrammatically, the piston being shown at I52. This piston I52 drives the crank shaft I63, which, in its turn, drives the outer internal gear I inside which rotate the small gears I05 which, in their turn. engage with the external gear I65. This gear I 65 is integral with the element I53. The propeller drive shaft I61 is driven by the small gears I85, which are mounted on a spider I58, so that the drive is from the crank shaft I53 through the gear I54 through the small pinions I55 to the spider I68, which spider is integral with the: propeller drive shaft I51. The torque reaction is thus taken by the element I53. Hence the pressure inside the cylinders I59 and I58 corresponds to the torque. In order to reduce this pressure to a more manageable value, the pipe I59 is connected into the chamber I10 in which reciprocates a small piston "I.

This piston "I is connected with the diaphragm I12 which forms the left hand wall of the chamber I50. Now the large pressure on the small piston "I must balance the low pressure on the large diaphragm I12. If there is leakage through the pipe I5I as is inevitable, the piston I'II moves to the right, uncovering the communication of an annular port I13 which is connected to a pipe I14 which discharges oil under pressure to the chamber I50. Therefore, when leakage takes place this leakage is made good by the oil supplied from the pipe I00 but the ratio of the pressure in I10 to the pressure in I50 is as the area I50 to the'area of I10.

The above description applies to the substitution of torque for M, A. P, in the mechanism shown in Figs. 1 and 5, and-when this is done the upper line of Fig. 3 is changed to that shown as AFWDIJ which indicates an advantage in favor of torque control over the M. A. P. control. The supercharger shifter is designed to shift at point F in the above case. If this torque control be substituted for M. A. P. in Figs. 2, 4 and 6 the advantage gained is not so marked. Using torque as a substitute for M. A. P. when a plied to the arrangement shown in Figs. 2, 4 and 8, the horse power no longer climbs (Fig. 4) from A to B, but follows the AHDKG line. The diaphragm correction device I which modifies the control of the inlet valve I20 will not be required. The auxiliary supercharger would be shifted into low speed ratio at point H and into high gear ratio at point D. In the case where the M. A. P. is used. it is to be noted that after passing the point B, (Fig. 4) the throttle I01 is wide open at all times and the power output thereafter is controlled by the throttle I23, Fig. 2 and by the gear shift. 0n the other hand when torque is used, the throttle I01 operates to control the torque from the point A to K and during this period the valve I35 operates to maintain a constant pressure equal to 25.5" of mercury in the chamber I03.

What I claim is:

1. In combination with an aircraft engine having a variable pitch propeller adapted to control the engine at a selected constant speed, manually operated control means for selecting said constant speed of the, engine, an engine driven supercharger, a change speed transmission therefor including a clutch, automatic clutch control means for said transmission comprising a snap action valve shifting mechanism, a servomotor valve connected thereto, a servomotor controlled by said valve, means controlled by the speed of the engine and by the pressure created by said supercharger and. by the atmospheric pressure to operate the snap action valve shifting mechanism to cause the servomotor to operate the clutch to change the relative speed of the supercharger at the desired combination of engine speed, manlfold air pressure, and altitude.

2. In an internal combustion engine for an airplane having a variable pitch propeller adapted to maintain the engine speed at a selected speed, the combination of a supercharger located in the airentrance, a throttle valve located in the air entrance to said supercharger, a second supercharger located on the engine side of said first supercharger and in series therewith a second throttle located in the entrance to said second supercharger, a carburetor located between the first and second superchargers, a single manually operated lever for selecting the desired engine speed, said lever being also connected to the sec- 0nd of the two throttles, means responsive to the air pressure existing on the engine side of said second supercharger known as the manifold air pressure and to the engine speed for first opening the second throttle to maintain a. selected manifold air pressure while operating with the first supercharger idle, the first throttle meanwhile being held open, and then, as the plane continues to ascend to the point where the second throttle has become wide open, means responsive to engine speed, atmospheric pressure and manifold air pressure for engaging the outer of the two superchargers in low speed the pressure of the inlet air entering the carburetor, means responsive to said inlet air pressure for regulating the said inlet pressure by controlling the first throttle so as to control the air pressure leading to the carburetor, further means responsive to diiierence between the air pressure in the inlet to the carburetor and the atmospheric pressure to modify the inlet pressure so that constant brake horse power is mainratio and thus raisingtained after said first supercharger becomes operative, further means responsive to the revolutions per minute of the engine, to the pressure of the atmosphere, and to the manifold air pressure for increasing th relative revolutions per minute of the first supercharger after the first throttle has become wide open in order to control the desired inlet air pressure as the plane continues to climb to higher altitudes.

3. In an internal combustion engine for an airplane having a'variable pitch propeller adapted to control the engine at a manually selected speed, a two speed supercharger therefor, a throttle valve in the inlet leading to said supercharger, automatic means for selecting the relative speed of the supercharger and the position of said throttle comprising a servomotor responsive to the conjoint action of the air pressure existing on the engine side of said supercharger known as the manifold air pressure, to the speed of the engine, and to the atmospheric pressure adapted to select the ratio of the supercharger drive, a second servomotor responsive to the conjoint action of the manifold air pressure, engine speed and to the difference between the manifold air pressure and the atmospheric pressure adapted to obtain a decreasing manifold air pressure with altitude so as to produce a constant brake horse power by controlling the position of the throttle.

4. In an internal combustion engine for an airplane having a variable pitch propeller adapted to control the engine at a manually selected speed and having torque responsive means, the combination of a two-speed supercharger therefor, a throttle valve located in the entrance leading to said supercharger, means including a servomotor for selecting the relative speed of the supercharger, said means being responsive to said engine torque responsive means, to the speed or the engine and to the atmospheric pressure, means including a servomotor for controlling th throttle admitting air to said supercharger, said means being responsive to engine speed and to torque tocontrol the throttle so as to maintain constant brake horse power.

5. In an airplane engine of the spark ignition type and having a variable pitch propeller adapted. to control the engine at a manually selected speed and having torque responsive means, including a servomotor for regulating the spark advance. said means being responsive to said torque responsive means and additional means responsive to the enat predeterminedvalues at every altitude and at each speed.

'7. In an internal combustion engine for an airplane having a variable pitch propeller incorporating speed responsive means adapted to control.

the engine at a manually selected speed, a second engine and by the'pressure created by said supercharger and by the atmospheric pressure to operate the snap action valve shifting mechanism to cause the servomotor to operate the clutch to change the relative speed of the supercharger at the desired combination of engine speed, manifold air pressure and altitude automatic means for controlling the spark advance, said means being responsive to engine speed and manifold air pressure, automatic means for controlling the throttle opening to maintain a desired brake horsepower, said means being responsive to engine speed, manifold air pressure and the difierence between manifold air pressure and the atmospheric pressure.

8. In an internal combustion engine for an airplane having a variable pitch propeller adapted to control the engine at a manually selected speed, a two-speed supercharger therefor, a throt: tle valve in the inlet leading to said supercharger, automatic means for changing the relative speed of the supercharger and the position of said throttle comprising a servomotor responsive to the conjoint action of the manifold air pressure existing on the engine side of said supercharger, to the speed of the engine, and to the atmospheric pressure and so constructed and arranged as to operate the speed changing means of the supercharger drive, a second servomotor responsive to the conjoint action of the manifold air pressure. and to the engine speed and so constructed and arranged as to control the position of the throttle so as to maintain a constant manifold air pressure.

a 9. In an internal combustion engine for an airplane having a variable pitch propeller adapted to control the engine at a manually selected speed gine speed for regulating said spark advance, said A means responsive to the torque opposing the] means responsive to the engine speed so that as the speed goes up, the spark is advanced, and as the torque is increased, the spark is retarded, so that the net advance or retard is the difference between thetwo.

6. In a supercharged airplane engine of the spark ignition type, having a variable pitch propeller adapted to control the engine at a manually selected speed and said engine having torque responsive means, automatic means responsive to the speed, a single manually operated lever adapte ed to control said speed. said automatic means being also responsive to torque and to atmospheric pressure and being adapted to control the spark advance, the'position of the throttle and to select the relative speed of the enginedriven supercharger, Whereby the horse power is maintained and having torque responsive means, the combination of a supercharger therefor, a throttle valve located in the entrance to said supercharger,

means including a servomotor so constructed and arranged as to control said throttle, said means being responsive to engine speed and torque to control said throttle so as to maintain constantbrake horsepower.

10. In an internal combustion engine for an airplane having a supercharger, a variable pitch propeller adapted to control the engine at a manually selected speed and having torque responsive means, the combination of a drive for said supercharger having two speeds and speed changing mechanism associated therewith, means including a servomotor for operating said speed chan ing mechanism, said means being responsive to said engine torque responsive means, to the speed of the engine, and to the atmospheric pressure.

' C. F. SCHORN. 

